Nuclear Targeting of Methyl-Recycling Enzymes in Arabidopsis thaliana Is Mediated by Specific Protein Interactions
Nuclear Targeting of Methyl-Recycling Enzymes in Arabidopsis thaliana Is Mediated by Specific Protein Interactions
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DOI：
10.1093/mp/ssr083
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发表时间：
2012-01-01
期刊：
影响因子：
27.5
通讯作者：
Moffatt, Barbara A.
中科院分区：
文献类型：
--
作者：
Lee, Sanghyun;Doxey, Andrew C.;Moffatt, Barbara A.
正常植物生长和发育需要许多转甲基反应。 S-腺苷高半胱氨酸水解酶 (SAHH) 和腺苷激酶 (ADK) 协同作用，回收这些反应的副产物，即 S-腺苷高半胱氨酸 (SAH)，否则该副产物会竞争性抑制甲基转移酶 (MT) 活性。在这里，我们报告了一些研究，以了解细胞核中产生的 SAH 如何被 SAHH 和 ADK 代谢。使用绿色荧光融合蛋白的定位分析表明，两种酶都能够定位到细胞质和细胞核，尽管在它们的序列中没有发现明显的核定位信号。删除分析表明，SAHH 的 41 个氨基酸片段 (Gly(150)-Lys(190)) 是该酶的核靶向所必需的。该片段表面暴露，显示出植物 SAHH 中独特的序列保守模式，并具有蛋白质-蛋白质相互作用基序的附加特征。 ADK 和 SAHH 在拟南芥中通过该片段相互作用，并且还与 mRNA 帽 MT 相互作用。我们认为该复合物的靶向是由 MT 的核定位信号引导的；其他 MT 可能类似地将 SAHH/ADK 靶向其他亚细胞区室，以确保不间断的转甲基作用。
Numerous transmethylation reactions are required for normal plant growth and development. S-adenosylhomocysteine hydrolase (SAHH) and adenosine kinase (ADK) act coordinately to recycle the by-product of these reactions, S-adenosylhomocysteine (SAH) that would otherwise competitively inhibit methyltransferase (MT) activities. Here, we report on investigations to understand how the SAH produced in the nucleus is metabolized by SAHH and ADK. Localization analyses using green fluorescent fusion proteins demonstrated that both enzymes are capable of localizing to the cytoplasm and the nucleus, although no obvious nuclear localization signal was found in their sequences. Deletion analysis revealed that a 41-amino-acid segment of SAHH (Gly(150)-Lys(190)) is required for nuclear targeting of this enzyme. This segment is surface exposed, shows unique sequence conservation patterns in plant SAHHs, and possesses additional features of protein-protein interaction motifs. ADK and SAHH interact in Arabidopsis via this segment and also interact with an mRNA cap MT. We propose that the targeting of this complex is directed by the nuclear localization signal of the MT; other MTs may similarly target SAHH/ADK to other subcellular compartments to ensure uninterrupted transmethylation.